PROJECT SUMMARY The role of the human microbiome in growth and development has become an intensive area of investigation and convincing data demonstrate that perturbations can influence growth in adults and in animals. Almost all work, however, has focused on the bacterial microbiome, and not on the even more abundant eukaryotic and prokaryotic virome. The virome, however, has equal or more potential to affect growth. In children under three years old, the great majority of infections are caused by viruses; these infections take both a metabolic toll and, on a more chronic level, have the potential to highjack endocrine, neurologic and metabolic systems. To date, however, very little is known about this essential component of the human metagenome. Prior studies on the virome: 1) have been limited as to body site investigated, 2) have not typically included healthy children, and 3) do not capture the dynamic changes in the virome occurring over time. Here we propose to use metagenomic next-generation sequencing (NGS) to analyze the gut, respiratory, and blood virome in serially collected samples from 86 children from birth to age 3, collected as part of a unique, multiethnic, pediatric cohort from northern California (the STORK study). A comparison group of 50 Bangladeshi children will also be assessed. Longitudinal sampling of the pediatric virome will reveal how the virome is initially established and changes over time. We hypothesize that establishment of a baseline virome and dynamic changes from birth to three years will have a significant impact in modulating growth in young children. Novel aspects of this project include: (1) longitudinal sampling of child from birth to age 3 years in the US, (2) simultaneous sampling of the virome in three body fluid compartments (blood, nasal swabs, and stool), (3) state-of-the-art metagenomic analysis by NGS coupled to a rapid bioinformatics pipeline, (4) accurate viral quantitation using a massively parallel NGS multiplexing approach and (5) ability to correlate viral findings with well-curated anthropometric, clinical and epidemiological outcomes data to search for associations, and with immunome and microbiome data generated in other projects to enable network analysis of host-microbial interactions. The proposed project will generate the most comprehensive and in-depth analysis to date of how the virome impacts growth in early life and has the potential to alter our approach to pathogenesis, prevention and treatment of childhood obesity.